Spinning Cylinder Research Articles

Design of Experiments-Based Optimization of an Electrochemical Decarboxylative Alkylation Using a Spinning Cylinder Electrode Reactor

Design of Experiments-Based Optimization of an Electrochemical Decarboxylative Alkylation Using a Spinning Cylinder Electrode Reactor

Amplification of electromagnetic fields by a rotating body

In 1971, Zel’dovich predicted the amplification of electromagnetic (EM) waves scattered by a rotating metallic cylinder, gaining mechanical rotational energy from the body. This phenomenon was believed to be unobservable with electromagnetic fields due to technological difficulties in meeting the condition of amplification that is, the cylinder must rotate faster than the frequency of the incoming radiation. Here, we measure the amplification of an electromagnetic field, generated by a toroid LC-circuit, scattered by an aluminium cylinder spinning in the toroid gap. We show that when the Zel’dovich condition is met, the resistance induced by the cylinder becomes negative implying amplification of the incoming EM fields. These results reveal the connection between the concept of induction generators and the physics of this fundamental physics effect and open new prospects towards testing the Zel’dovich mechanism in the quantum regime, as well as related quantum friction effects.

Optimization of system parameters during conjugate mixed convective flow in a square domain with an oscillating spinning cylinder

A computational analysis has been executed to analyze the combined conduction-mixed convection heat transfer of a rotationally oscillating solid cylinder in a differentially heated square box filled with air. The conjugate mixed convective flow initiates the heat transfer process, where the left-side boundary is isothermally kept to a higher temperature, and the right-side boundary is maintained at a lower temperature. Conduction heat transfer takes place inside the solid cylinder. Navier-Stokes and heat energy conservation equations model the system in the dimensionless pressure-velocity formulation. All these equations are solved via the Galerkin finite element approach. Three different combinations of Grashof (103-105), Reynolds (32–316), and Richardson (0.1–10) numbers are examined to systematically investigate the variations of governing parameters on instantaneous Nusselt numbers and the respective time-averaged values along the hot wall. In each combination, the impacts of the oscillating amplitude and frequency and the variation of cylinder diameter are examined to perform the optimization study. Power spectrum analysis is also done using the Fast Fourier Transform in the frequency domain to visualize the principal frequency of the system. The instantaneous values of the Nusselt number exhibit a wavering pattern over time owing to the recurrent waning and waxing of the thermal boundary layer. For all the cases, the maximum diameter and oscillating amplitude of the cylinder are found to maximize the heat transfer. However, the optimized frequency of the oscillation strongly depends on the selection of the governing parameters. In addition, the principal thermal frequency of the system is determined to be independent of the oscillation frequency.

Energy Inventory in the Sliding and Rolling Regimes

The energy inventory during the transition between the sliding and rolling regimes has frequently received short shrift in the physics and engineering literature. Here we delve into the intricacies of sliding and rolling motion and emphasize the salient points often missed in a cursory analysis which tends to focus mostly on torque and angular momentum. We show, for instance, that when a spinning cylinder slides and skids and ends up rolling, it loses two-thirds of its initial kinetic energy doing work against friction. Moreover, this number is independent of the coefficient of friction! This sounds counterintuitive at first blush. We help the reader develop an intuition for these counterintuitive rolling and sliding scenarios by a simple comparison that will remind the reader that they have seen this concept in a more familiar context before. When a car slams on the brakes and skids to a stop the loss of the initial kinetic energy to heat is not dependent on the coefficient of friction. If the coefficient of friction increases the stopping distance decreases and vice versa but the kinetic energy lost to heat remains the same. The more mysterious aspect in the rolling/sliding cylinder is the exact factor 2/3 regardless of the coefficient of friction. We have programmed an app with App Inventor to simulate various scenarios in order to help develop the intuition which we have found lacking in students of physics and engineering.

Mixed convection phenomenon for hybrid nanofluid flow exterior to a vertical spinning cylinder with binary chemical reaction and activation energy

The study of hybrid nanofluids over spinning cylindrical configurations is widely used in numerous engineering and technological applications. Compared to conventional coolants, nanofluids explore superior thermal conductivities and thereby promote outstanding heat transport capabilities. In this study, hybrid nanofluid flow and thermal transmission across a vertical spinning cylinder are examined in the presence of an externally applied transverse magnetic field. The working fluids used are Ag/water nanofluid and Al2O3-Ag/water hybrid nanofluid. The analysis of heat transmission is carried out in the presence of slip and convective conditions, nonlinear thermal radiation, activation energy, and viscous dissipation. Partial differential equations (PDEs) are used to model the physical situation and are subsequently transformed into ordinary differential equations (ODEs). Through the use of MATLAB's bvp4c technique for ODEs, graphical and computational results are produced and validated with previously reported studies. The important findings are that the flow field diminishes as the magnetic field parameter and Reynolds number increase. Further, for larger levels of nano particle's fraction and thermal Biot number, the thermal features increase. Moreover, it is noted that the mass diffusion rate is lowered by the system's activation energy.

Numerical simulation of the dynamical behavior of a spinning cylinder partially filled with liquid

The flow pattern and transient response of a spinning cylinder partially filled with fluid are investigated in this paper. A two-dimensional finite element model of the fluid domain in the cylinder cavity is developed via the structured tetrahedral element. By using the volume of fluid model, the flow pattern of the liquid is examined numerically. Also, the effects of fluid type, rotating speed, and liquid height on the flow pattern are investigated. Then, the obtained fluid pressure exerted on the inner wall of the cylinder is considered as the input load, and transient dynamic analysis of the spinning liquid-filled cylinder is carried out. Finally, a comprehensive parametric study is conducted to evaluate the effects of liquid type, spinning speed, and fluid height on the dynamical behavior of the system. The results show that these parameters greatly influence the fluid flow pattern and dynamic characteristics of the spinning liquid-filled cylinder system.

MHD forced convection flow in an infinite channel with a rotating cylinder

The numerical investigation of forced convection flows under the influence of a uniform magnetic field is carried out in an infinite channel with an isothermal rotating circular cylinder placed in the center of the channel. The problem is discretized using the dual reciprocity boundary element method with constant elements. The analysis is done on how the controlling parameters affect both the fluid flow and heat transfer properties. It is observed that increasing the intensity of the magnetic field suppresses the impact of the rotational cylinder and decreases the flow velocity at the center while it enhances the heat transfer rate which causes a rise in the average Nusselt number along the heated walls. On the other hand, the heat transfer rate along the horizontal walls is an increasing or decreasing function of the rotational velocity of the cylinder, and the direction of cylinder rotation causes the boundary layers to become thicker or thinner close to the heated surfaces. Thus, the combined effects of the spinning cylinder and the magnetic field can be used to regulate the characteristic of fluid flow as well as the thermal topology of an infinite channel.

Mixed Convection Flow and Heat Transfer of Two Rotating Cylinders in a Trapezoidal Enclosure Filled with Porous Medium

The goal of this research is to investigate numerically mixed convection flow and heat transfer characteristics from two rotating cylinders in a trapezoidal enclosure filled with porous material for a variety of factors including rotation speed and direction, Richardson number, and the location of the cylinders. The results of this presentation were checked against accessible data and determined to be very similar. The heat transmission properties within the trapezoid were found to be substantially dependent on the Richardson number, speed, and direction of the spinning cylinders, as well as the location of the cylinders according to the findings of this study. Furthermore, it was discovered that the CW-CW casing produced more heat transfer as compared to the CCW-CW scenario for various Richardson numbers when the cylinders placed vertically. Furthermore, this research revealed that, for higher Richardson values, the rotation speed has no effect on the heat transfer increase inside the trapezoidal enclosure. The effect of the cylinders’ location on the average Nusselt number was also studied in this investigation. It was found the placing the cylinders in the vertical direction produced higher heat transfer compared with horizontal location for a trapezoid heated from below.

CFD analysis of turbulent forced convection over a spinning cylinder in an enclosed channel

• More practical scenario of speed ratio has been used in this study • Blockage ratio affects both the flow and thermal fields • Rotational velocity and direction do not affect the flow or thermal field • Bulk flow Reynolds number influences both thermal and flow fields • Pressure drag dominates over viscous drag at higher Reynolds number A CFD approach has been used to analyze fully developed turbulent flow and heat transport over a spinning hot circular solid cylinder inside an enclosed channel. The finite element approach is used to solve the Reynolds-Averaged Navier-Stokes and energy equations and the shear stress transport model. The flow is explored for various Reynolds numbers ranging from 3 × 10 3 to 10 7 with the blockage ratios of 0.05, 0.1, and 0.15 along with the variation of speed ratios of the rotating cylinder. This study found that the direction and speed of the cylinder have an insignificant effect on thermo-fluid characteristics. On the other hand, the drag coefficient decreases while the average Nusselt number increases to a specific value of Reynolds number and then becomes almost constant. Effectiveness increases for a lower Reynolds number and then becomes stable. The heat performance of the rotating cylinder for the stationary one and the contributions of pressure drag are presented here.

Nonlinear buoyancy driven flow of hybrid nanoliquid past a spinning cylinder with quadratic thermal radiation

The buoyancy driven flow on a vertical cylinder finds relevance in many engineering applications as in geophysics, chemical engineering, metallurgy, oceanography etc. The flow of water transporting hybrid nanoparticles (25 nm Ag and 40 nm MgO) around a spinning cylinder surface subjected to quadratic radiative heat transfer is explored using nonlinear buoyancy-induced (quadratic convection). The Esfe models for thermal conductivity and dynamic viscosity as a function of a volumetric percentage of nanoparticle are amalgamated. The partial differential equations (PDEs) for buoyancy driven boundary layer flow are used to construct the dimensionless nonlinear form of governing PDEs, which are then solved by discretization method i.e., 2D Galerkin Finite Element Method (GFEM). Heat transport is found to be greater for quadratic radiation/convection than for linear thermal radiation/convection. Using response surface methodology, the maximum average heat transport (5.78391) is achieved for maximum parametric value of buoyancy parameter, rotating parameter and radiation parameter. Residual and sensitivity analyses are conducted for quadratic fitting. In addition, sensitivity of average Nusselt number towards radiation parameter is always positive.

Stability analysis of spinning liquid-filled cylinders with exponentially varying cross section

In this paper, the stability analysis of a spinning liquid-filled cylinder with exponentially varying cross sections is carried out. Based on the spinning Euler–Bernoulli beam theory, the governing equation for vibration of the spinning cylinder is formulated by using Hamilton's principle. The relative perturbation motion equation of the rotating fluid is derived using the composition theorem of acceleration. Combined with the flow boundary conditions, the fluid forces exerted on the cylinder are obtained. Using the analytical method, the characteristic frequency equation of the system is determined. The stability of the considered system is determined by eigenvalue analysis. The accuracy of the proposed model is validated by comparing it with the existing data in the literature. Finally, a detailed parameter study is conducted to demonstrate the effects of mass ratio, cavity ratio, taper parameter, thickness ratio, and axial position on the vibration and stability of the system. The results show that these parameters play an important role in the instability, natural frequency, and critical spinning speed of the spinning taper cylinder partially filled with liquid.

Nonreciprocal light propagation induced by a subwavelength spinning cylinder.

Nonreciprocal optical devices have broad applications in light manipulations for communications and sensing. Non-magnetic mechanisms of optical nonreciprocity are highly desired for high-frequency on-chip applications. Here, we investigate the nonreciprocal properties of light propagation in a dielectric waveguide induced by a subwavelength spinning cylinder. We find that the chiral modes of the cylinder can give rise to unidirectional coupling with the waveguide via the transverse spin-orbit interaction, leading to different transmissions for guided wave propagating in opposite directions and thus optical isolation. We reveal the dependence of the nonreciprocal properties on various system parameters including mode order, spinning speed, coupling distance, and various losses. The results show that higher-order chiral modes and larger spinning speed generally give rise to stronger nonreciprocity, and there exists an optimal cylinder-waveguide coupling distance where the optical isolation reaches the maximum. The properties are sensitive to the material loss of the cylinder but show robustness against surface-roughness-induced loss in the waveguide. Our work contributes to the understanding of nonreciprocity in subwavelength moving structures and can find applications in integrated photonic circuits, topological photonics, and novel metasurfaces.

Habitat Bennu: Design Concepts for Spinning Habitats Constructed From Rubble Pile Near-Earth Asteroids

The authors explore the possibility that near-earth, rubble pile asteroids might be used as habitats for human settlement by increasing their rotation to produce spin gravity. Using previously published scaling by Maindl et al. and studies of asteroid populations, it is shown that there is no class of hollowed body that would survive the spin-up process on its own without additional reinforcement. Large solid-rock asteroids (diameterD> 10 km) would not have the tensile strength to withstand the required rotation rates and would fracture and break apart. Smaller asteroids, being ‘rubble piles’, have little tensile strength and would quickly disperse. The possibility of containing the asteroid mass using higher-strength materials like carbon nanofiber is instead considered. It is found that a moderate tensile strength container can maintain the integrity of a large spinning cylinder composed of dispersed asteroid regolith. The research extends the range of possible asteroid habitat candidates, since it may become feasible to construct habitats from the more numerous smaller bodies, including NEAs (Near Earth Asteroids). The required tensile strength of the container material scales with habitat radius and thickness and is ∼ 200 MPa for a starting asteroid body of radius 300 m that is spun up to provide 0.3 g⊕while increasing its radius to 3 km and maintaining a rubble and regolith shield thickness of 2 m to protect against cosmic rays. Ambient solar power can be harvested to aid in spin-up and material processing.

Utilizing the Magnus effect to produce more downforce than a standard wing

Wings on cars help keep the vehicle grounded at high speeds and improve traction by producing downward force known as downforce. To generate more downforce, the wings generally need a high angle of attack which leads to increased drag. A car’s performance is degraded with drag by the increase in air resistance, so a new method of generating downforce with better drag performance could be beneficial. The Magnus effect is the tendency of a spinning cylinder or sphere to produce force perpendicular to the flow of the air. Cylinders undergoing the Magnus effect have been found to have less drag than comparable wings and can generate lift and downforce with sufficient airflow. Thus, we saw it fit to test if a spinning cylinder was capable of generating more downforce than a typical wing via the Magnus effect. Based on the success of the Magnus effect for lift, we hypothesized similar outcomes when testing for downforce. We tested for downforce by attaching a motor-driven cylinder to a scale and used a leaf blower to simulate high wind speeds. We also tested a standard wing as a control. Overall, we found that at all speeds, the cylinder was significantly more effective at producing downforce with nearly 50% more force produced at the highest velocity while outperforming the wing by larger margins at lower speeds. Our experiments demonstrated that cylinders could be a potential replacement for the wing when downforce is a priority.

Robust exceptional point of arbitrary order in coupled spinning cylinders.

Exceptional points (EPs), i.e., non-Hermitian degeneracies at which eigenvalues and eigenvectors coalesce, can be realized by tuning the gain/loss contrast of different modes in non-Hermitian systems or by engineering the asymmetric coupling of modes. Here we demonstrate a mechanism that can achieve EPs of arbitrary order by employing the non-reciprocal coupling of spinning cylinders sitting on a dielectric waveguide. The spinning motion breaks the time-reversal symmetry and removes the degeneracy of opposite chiral modes of the cylinders. Under the excitation of a linearly polarized plane wave, the chiral mode of one cylinder can unidirectionally couple to the same mode of the other cylinder via the spin-orbit interaction associated with the evanescent wave of the waveguide. The structure can give rise to arbitrary-order EPs that are robust against spin-flipping perturbations, in contrast to conventional systems relying on spin-selective excitations. In addition, we show that higher-order EPs in the proposed system are accompanied by enhanced optical isolation, which may find applications in designing novel optical isolators, nonreciprocal optical devices, and topological photonics.

Parametric Study of Magnus Wind Turbine with Spiral Fins using BEM Approach

The aim of this work is to carry out an aerodynamic analysis to assess the power and identify the characteristics of the horizontal axis Magnus type wind turbine with spiral fins. A parametric study is achieved to analyze the effects of the different influence parameters such as the turbine tip speed ratio, the cylinder spinning ratio, the blade aspect ratio and the cylinder hub-tip ratio. The analysis approach adopted in this study is the Blade Element Momentum BEM using the experimental lift coefficient data for the configuration of spinning cylinders with spiral fins. In this analysis, losses are not taken in consideration. Both axial and angular interference coefficients are evaluated for this type of wind turbine. The former is assessed by solving a quadratic equation and the latter is calculated from a classic formulation including the term of spinning. An iterative process is followed to achieve this task. Concerning the obtained results, the aerodynamic characteristics of the Magnus wind turbine, analyzed in this study, provide some elucidation to lead a successful preliminary design of this novel type of machine.

Radiative swirl motion of hydromagnetic Casson nanofluid flow over rotary cylinder using Joule dissipation impact

In this article, the heat transfer is examined in spinning flow of the Casson nanofluid. The spinning motion is produced with the help of stretching and rotating cylinder. In current work two cases, both for constant and variant axial temperature over the exterior of the spinning cylinder are studied. For controlling the rate of heat transfer, some heat effects such as heat generation/absorption, Joule heating and thermal radiations have been considered for flow system. For investigation the influence of thermophoretic force and Brownian motion exerted by Casson nanofluid, the famous Buongiorno model has been employed. The modeled equations have converted to dimensionless form using a set of similar variables. To improve the solution convergence of flow equations a compressed variable is also employed. As the main outcome of this work, it has observed that, with growing values of Reynolds number and magnetic parameter the flow characteristics reduce in all directions. A growth in temperature profile is also observed for constant wall temperature (CWT), while a reduction is noticed in temperature profile for prescribed surface temperature (PST). Moreover, the concentration of fluid reduces with growing values of Prandtl and Lewis numbers.

Direct numerical simulation of a non-equilibrium three-dimensional turbulent boundary layer over a flat plate

Abstract

Analysis of geometric uncertainties in CFD problems solved by RBF-FD meshless method

In order to analyze incompressible and laminar fluid flows in presence of geometric uncertainties on the boundaries, the Non-Intrusive Polynomial Chaos method is employed, which allows the use of a deterministic fluid dynamic solver. The quantification of the fluid flow uncertainties is based on a set of deterministic response evaluations, which are obtained through a Radial Basis Function-generated Finite Differences meshless method. The use of such deterministic solver represents the key point of the analysis, thanks to the computational efficiency and similar accuracy over the traditional mesh-based numerical methods. The validation of the proposed approach is carried out through the solution of the flow past a 2D spinning cylinder near a moving wall and the flow over a backward-facing step, in presence of stochastic geometries. The applicability to practical problems is demonstrated through the investigation of geometric uncertainty effects on the forced convection of Al2O3-water nanofluid laminar flow in a grooved microchannel.

Optimization of spinning process parameters for the large-diameter thin-walled cylinder based on the drum shape

Thinning spinning has the advantage of enhancing the performance of a product, and it is an effective method for manufacturing large-diameter ultrathin cylindrical parts. However, the rigidity of a large-diameter ultrathin wall cylinder is poor, the spinning process and forming quality are sensitive to the process parameters, and the drum-shaped result of the spinning process is prone to instability, which can cause the spinning process to be unbalanced. Therefore, it is a great challenge to select the appropriate process parameters for achieving the long-range stable spinning of large-diameter ultrathin wall cylinders. Based on the analysis of the thin-walled cylinder spinning mechanism, this study analyzed the effects of key process parameters on the drum shape of a C-276 thin-walled cylinder spinning process by serial experiments. The results of serialization experiments show that the thinning rate has a great influence on the spinning process state, the feed rate is secondary, and the speed has the least influence. On the basis of experimental analysis, the optimized process parameters of thin-walled cylinder spinning are obtained by using the support vector machine method: the wall thickness reduction rate cannot exceed 45% in single-pass spinning; 30~40% is a reasonable choice interval; the feed rate can range from 0.8 to 1.0 mm/r; and the rotation speed can range from 80 to 100 r/min. Finally, a comparative experiment and stability test of thin-walled cylinder thinning spinning over a long range is carried out, which verifies that the optimized spinning parameters can be used for the long-range stable spinning of large-diameter ultrathin cylinder parts.